The invention relates generally to differential pressure sensing devices and, more particularly, to a mounting and fluid pressure transfer support for supporting and transmitting fluid pressure to a differential pressure sensing mechanism.
In process industries (refineries, chemical plants, gasoline plants and the like) it is common that the flow of liquids within process pipes be measured and visually displayed as an available guide to the operating personnel of the condition of the process at all times. Although there are many ways in which the flow of liquid within a process line may be measured, one of the more economical methods for remote sensing and transmission of the liquid flow in the form of appropriate signals to an operating facility lies in the use of devices that measure the difference in pressure upstream and downstream of a restrictive device called an orifice plate held in place by a pair of flanges tapped to permit pressure measurement. Such fluid measuring devices are commonly referred to as differential pressure transmitters or d/p cells. The measured differential pressure is converted to a signal readable in terms of flow rate for either automatic control or for operator observation only. The instrument, therefore, will transmit a signal proportional to the pressure difference between the two taps for which the instrument is calibrated.
As noted in my prior U.S. Pat. No. 2,871,881, issued Feb. 3, 1959, differential pressure sensing mechanisms, commonly referred to as d/p cells, are generally mounted adjacent to the process line with which it is associated by providing a length of pipe, frequently of 2-inch diameter, that is securely cemented or otherwise fixed in position in order to provide a vibration free support structure. The d/p cell is then mounted on the 2-inch pipe structure by means of U-bolts or other suitable securing devices, with tubing or small bore pipe, such as 1/2-inch pipe, serving as the process conduit, and connecting the sensing element to the tapped flange of the process line. The 2-inch pipe stand may be welded to a nearby structural member or to the process line itself or may be supported in concrete.
A common manner of installing differential pressure sensing transmitters through the use of manifold connection devices typically involves mounting of a d/p transmitter on a 2-inch pipe stand by means of a suitable bracket and locking the transmitter to the pipe stand with a U-bolt. A manifold transmitter assembly is connected to process flange valves with pipe or tubing, typically 1/2-inch pipe or tubing. The transmitter, thus supported by the pipe, stand provides support for the manifold structure. Differential pressure transmitters and manifolds mounted in this manner present a disadvantage from the standpoints of installation, repair, cleaning and other servicing. It is necessary to remove the transmitter from the pipe stand for servicing, also requiring the manifold to be disconnected from the transmitter.
Another problem created by this character of installation concerns possible damage to d/p transmitters after installation and prior to plant start up. The d/p transmitter must be available to complete the piping installation because it must provide support for the manifold, and, therefore, is frequently subjected to the elements and to hazards of the construction operation for extended periods of time. It would be desirable to provide the piping connection from the process to the manifold and to connect the d/p transmitter to the manifold just prior to plant start-up for instrument check-out and calibration. In this manner, the expensive and delicate instrument can be adequately protected by its container until needed for plant start-up.
In accordance with the present invention, however, it is proposed to provide a support for the d/p cell that enables the cell to be easily removed in order to clean or replace the cell as a unit, and to further provide an intermediate support body that may be installed independently of the cell. Such independent installation of the intermediate support body may be performed by the pipefitter while allowing subsequent attachment of the cell by the instrument technician.
Thus, there is provided an assembly comprising an upstanding structure such as a 2-inch diameter pipe that is fixed in position adjacent the process vessel. A plate-like base member is releasably attached to the pipe by a pair of U-bolts. A support member, including valves, flow lines, and passageways, is then attached to the base member. This construction and assembly may be performed by the pipefitter and without the necessity of becoming involved with the the arranging of the d/p cell itself. Thus, the intermediate support member once installed by the pipefitter includes means for attaching thereto at a later point in time the d/p cell by the instrument technician.
It is a primary object of this invention, therefore, to provide a novel mounting support serving as an interfacing connection between a process orifice flange union or process vessel and a differential pressure sensing instrument in addition to providing structural support for the instrument.
It is another object of this invention to provide a novel mounting support construction that simply and positively establishes structural support for differential pressure sensing apparatus and further serves to transmit fluid pressures from a process flow line or vessel to the pressure sensing mechanism.
Among the several objects of this invention is contemplated the provision of a novel mounting support structure which provides process connections to both the high and low signal sides of a differential pressure sensing instrument and provides for complete removal of the instrument for repair without disturbing the process piping in any manner.
The above and other objects and novel features of the instant invention will be readily apparent from the following description taken in conjunction with the accompanying drawings. It is to be expressly understood that the drawings are for the purpose of illustration and are not intended to define the limits of the invention but rather to merely illustrate preferred embodiments and structures incorporating the features of the instant invention.